Thursday, December 29, 2011

One night late in December, a small group of us decided to check out Puget Sound at Seahurst during a minus 1.5 foot low tide. At extreme low tides, you can find all sorts of marine invertebrates close up and personal. Unfortunately, low tides occur at night during the winter, so you have to go out with a strong flashlight and, most of the time, bundled up in parka and rain gear to have this experience. We were lucky: moderate temperature, no wind, no rain at 10 pm. The water was calm and clear as a windowpane, and the exposed beach was covered with critters.

It takes a while to get the hang of it. You have to distinguish stationary animals, many of them sessile filter-feeders, from multi-hued rocks and gravel and sand. Many of them are exposed by the receding tide, while others shelter in crevices, among algal fronds, or under rocks. On this visit, we looked mostly on the surface, as there were very few rocks of the right size to turn. But by doing this, you can find many more critters, including several species of fishes. But always replace the rocks carefully!

Mollusks of numerous kinds, including limpets, lined chitons (Tonicella lineata) and rock oysters (Pododesmus cepio), were scattered over the large boulders that were exposed by the low tide. There were scattered plumose anemones (Metridium senile) hanging down obscenely from rocks and Christmas anemones (Urticina crassicornis) looking like prettily patterned blobs. We found one attached to a movable rock, so we took it out in a foot of water to let it expand. We came back to it 10 minutes later, and it was nicely expanded for photos.

As we were photographing it, a kelp crab (Pugettia producta) approached from stage right. It came up to the anemone and started feeling in its tentacles. We wondered if it might be snipping them off to eat, but we couldn't be sure. More likely it was feeling for organic matter left among the tentacles, perhaps part of the anemone's last meal. Several times after inserting a cheliped among the tentacles, it brought it back to its mouth. After a short while of doing this, it started running one of its longer legs through the tentacles, almost in a grooming manner. Perhaps the leg was able to detect food particles?

Presumably the thick chitin of the crab's legs protected it from the anemone's stinging cnidocytes, and a coating of anemone mucus might have conferred additional protection.

As we were watching this, a red rock crab (Cancer productus) approached the kelp crab, and it scuttled away about a meter and sat among the eelgrass. The second crab didn't interact with the anemone but then found a dead Dungeness crab (Cancer magister), perhaps to check it out as dinner, but our lights may have scared it away. We had earlier found a pair of Dungeness crabs mating in an eelgrass bed.

Sea stars were the most conspicuous megafauna appearing in our lights, including sunflower stars (Pycnopodia helianthoides), many of them young, and ochre sea stars (Pisaster ochraceus), with fewer mottled sea stars (Evasterias troschelii). We turned one Pycnopodia over that had a hump in the middle and found what I thought was a fish skull clutched in its hot little tube feet. We grabbed the skull and started pulling on it and out from what must be an amazingly large stomach came a spotted ratfish (Hydrolagus colliei) carcass, largely digested!

On a previous occasion at the same site, we had found a Pycnopodia that had ingested a whole rat. We assumed the rat had been dead in the water rather than that the starfish had gone on walkabout up in the rocks. This huge sea star really seems at the top of the intertidal Puget Sound food chain!

Tuesday, December 13, 2011

One of the more spectacular natural phenomena of the Pacific Northwest is the annual spawning of five species of Pacific salmon (Oncorhynchus).

The Harrison River is one of the major tributaries of the Fraser River in southwestern British Columbia. Every fall my wife and I make a pilgrimage to the Harrison to see this phenomenon. The salmon are spectacular to watch, although we see very little actual spawning, just the great number of fish, both alive and dead. The dead ones have presumably spawned, as Pacific salmon spawn only once in their life and then die.

The attribute of breeding only once is called semelparity, and it is more typical of organisms that live only one year, usually called "annuals." There are many annual plants among our wild flowers and quite a few annual animals as well, mostly small ones. Hatch or sprout, grow rapidly, breed. and die are the usual course of events for an annual animal or plant.

Pacific salmon, on the other hand, have a fairly complex life cycle. They hatch in fresh water, where they may spend up to a few years, then move into the marine environment, where over an additional few years those that survive grow large and strong, prepared to come back to the river system and the very stream where they were hatched. They swim upriver some distance, spawn, and then die. That's what all those salmon are doing in the Harrison River.

Some of them are there because of human activities. Hatcheries on tributaries of the Harrison raise the young fish in tanks, where they are protected from predators, then release them when they are ready to travel downstream. When they come back as breeding adults, they are captured and bred artificially by applying sperm extracted from the males to eggs extracted from the females, and the cycle begins again.

The Harrison River system has many thousands of fish of four salmon species—chinook (O. tshawytscha), coho (O. kisutch), chum (O. keta) and sockeye (O. nerka). You'll notice the scientific names from Russian; all of our species occur as well on the other side of the Pacific Ocean.

When very large runs are in the river system, especially from October to December, the dead and dying fish support great populations of predators and scavengers. Among them are gulls, crows, ravens, and—most notably—Bald Eagles.

Eagles come to the Harrison in the late fall by the thousands. I have estimated as many as 500 visible from one spot, although that was a rare sighting. More likely, a visitor who stops at several places along the river may see a few hundred birds, sometimes a dozen roosting in the same tree or a hundred spread out over the river flat.

Interactions among the birds are commonplace and make the experience a memorable one. The whistled calls of the eagles, the flowing river, the conifer background, and, if you're lucky, the blue sky, all make the experience a memorable one. The smell of rotting salmon carcasses adds an extra dimension not available on all nature trips.

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About the Slater Museum

Our goals are to preserve and provide a collection of specimens to be used for research and education. Located in Tacoma, Washington, the Slater Museum is one of the region's significant repositories for bird, mammal, reptile, amphibian and plant specimens from the Pacific Northwest. In addition, we strive to educate the local community about nature and about the value of museums.